Java Reference
In-Depth Information
of occupied buffer cells, the contents of the buffer cells and the current
writeIndex
and
readIndex
. Line 51 invokes method
notifyAll
to allow any
Producer
threads
waiting to
write
into the
CircularBuffer
object to attempt to write again. Then line 53 returns the
consumed value to the caller.
CircularBuffer
Method
displayState
Method
displayState
(lines 57-86) outputs the application's state. Lines 63-64 output
the values of the buffer cells. Line 64 uses method
printf
with a
"%2d"
format specifier
to print the contents of each buffer with a leading space if it's a single digit. Lines 71-83
output the current
writeIndex
and
readIndex
with the letters
W
and
R
, respectively. Once
again,
displayState
is a synchronized method because it accesses class
CircularBuffer
's
shared mutable data.
Testing Class
CircularBuffer
Class
CircularBufferTest
(Fig. 23.19) contains the
main
method that launches the ap-
plication. Line 12 creates the
ExecutorService
, and line 15 creates a
CircularBuffer
ob-
ject and assigns its reference to
CircularBuffer
variable
sharedLocation
. Line 18
invokes the
CircularBuffer
's
displayState
method to show the initial state of the buf-
fer. Lines 21-22 execute the
Producer
and
Consumer
tasks. Line 24 calls method
shutdown
to end the application when the threads complete the
Producer
and
Consumer
tasks and
line 25 waits for the tasks to complete.
1
// Fig. 23.19: CircularBufferTest.java
2
// Producer and Consumer threads correctly manipulating a circular buffer.
3
import
java.util.concurrent.ExecutorService;
4
import
java.util.concurrent.Executors;
5
import
java.util.concurrent.TimeUnit;
6
7
public
class
CircularBufferTest
8
{
9
public
static
void
main(String[] args)
throws
InterruptedException
10
{
11
// create new thread pool with two threads
12
ExecutorService executorService = Executors.newCachedThreadPool();
13
14
// create CircularBuffer to store ints
CircularBuffer sharedLocation =
new
CircularBuffer();
15
16
17
// display the initial state of the CircularBuffer
18
sharedLocation.displayState(
"Initial State"
)
;
19
20
// execute the Producer and Consumer tasks
21
executorService.execute(
new
Producer(sharedLocation));
executorService.execute(
new
Consumer(sharedLocation));
22
23
24
executorService.shutdown();
25
executorService.awaitTermination(
1
,
TimeUnit.MINUTES
);
26
}
27
}
// end class CircularBufferTest
Fig. 23.19
|
Producer
and
Consumer
threads correctly manipulating a circular buffer. (Part 1 of 3.)
